Majority Vote - Amazon Top Interview Questions
Problem Statement :
You are given a list of integers nums containing n integers, where each number represents a vote to a candidate.
Return the id of the candidate that has \gt \lfloor \frac{n}{2}\rfloor>⌊
2
n
⌋ votes. If there's not a majority vote, return -1.
This should be done in \mathcal{O}(1)O(1) space.
Constraints
n ≤ 100,000
Example 1
Input
nums = [5, 5, 1, 1, 2, 2, 2, 2, 2]
Output
2
Example 2
Input
nums = [3, 3, 4, 4]
Output
-1
Explanation
Neither 3 or 4 have more than 2 votes.
Solution :
Solution in C++ :
int solve(vector<int>& nums) {
int n = nums.size();
if (n == 1) return nums[0];
if (n < 0) return -1;
int maj = nums[0];
int count = 1;
for (int i = 1; i < n; i++) {
if (count == 0) {
maj = nums[i];
count++;
} else if (maj == nums[i]) {
count++;
} else {
count--;
}
}
// we can not be sure if there is a majority element so
// getting a second loop to check wether the element is majority or not
int c1 = 0;
for (int i = 0; i < n; i++) {
if (nums[i] == maj) {
c1++;
}
}
if (c1 > (n / 2)) return (maj);
return -1;
}
Solution in Python :
class Solution:
def solve(self, nums):
nums.sort()
n = len(nums)
check = nums[n // 2]
count = nums.count(check)
if count > n // 2:
return check
else:
return -1
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